Role of residual stresses induced by industrial fabrication on stress corrosion cracking susceptibility of austenitic stainless steel

Effect of residual stress generated during tube fabrication, roll expansion and machining of stainless steel on the stress corrosion cracking (SCC) susceptibility was studied by testing fabricated tubes, tube–tube sheet joint and heavily machined plate of austenitic stainless steel (SS) in boiling MgCl₂. U bend samples of machined plate were exposed to acidified SO₄ + Cl^? environment at room temperature to study its ambient temperature SCC behavior. The results correlate the SCC behavior of the SS tubes and roll expanded joints to the nature and magnitude of residual stresses present. The study also highlights the distinct difference in ambient temperature SCC behavior of machined vs. nonmachined surfaces.     

Sorption of Tertiary Butyl Mercaptan to Indoor Materials in Contact with Air or Water

This study reports sorption of the malodorant 2-methyl-2-propanethiol, commonly known as tertiary butyl mercaptan (TBM), to selected indoor materials. The phase distribution of TBM in gas-solid and aqueous-solid systems was evaluated using batch reactors. Sorbents used in the study included two carpets, two wallpapers, a soil, and granular activated carbon (GAC). Sorption was studied for gaseous and aqueous TBM concentrations spanning three orders of magnitude and contact times ranging from 1 to 28 days. The phase distribution data were plotted and fitted using linear and Freundlich relationships. Results indicated that all solids sorbed environmentally significant quantities of TBM, with the likelihood of producing concentrations above the odor threshold during subsequent remediation using mechanical ventilation. TBM retention by sorbents was greater from air than from water. The malodorant partitioned readily into wallpapers and slowly into the carpet materials. Sorption was nonlinear in the case of GAC and the nonlinearity appeared to increase with sorption contact time. GAC sorbed TBM strongly from both air and water.     

Breakdown Trade-Off Relation of Mechanical Properties via Micro-alloying in Mg–Mn Alloys

The impact of micro-alloying on tensile behavior at strain rates in various ranges is examined using five types of extruded Mg-0.3 at. pct Mn–0.1 at. pct X ternary alloys, where X is selected as a common element, Al, Li, Sn, Y or Zn. Microstructural observations reveal that the average grain size of these extruded alloys is between 1 and 3 μm, and these micro-alloying elements segregate at grain boundaries. In room temperature tensile and compression tests, these results show that the mechanical properties and deformation behavior are influenced by the micro-alloying element, even as a small addition of 0.1 at. pct. Mg–Mn–Y and Mg–Mn-Zn alloys show higher strength and smaller strain rate sensitivity (m-value) among the present alloys, owing to the rate-controlling mechanism as dislocation slip. On the other hand, the Mg–Mn–Li alloy exhibits the largest elongation to failure in tension and the highest strain rate sensitivity, associated with high contribution of grain boundary sliding to deformation. These differences are due to the grain boundary segregation of the micro-alloying elements. Compared to the common Mg alloys, the present ternary alloys also show a trade-off relationship between strength and ductility, which is similar to that of the well-known Mg alloys; however, these properties of the Mg–Mn system ternary alloys could be controlled via the type of micro-alloying elements with a chemical content of 0.1 at. pct.

     

Variations on the Theme of Scarf's Counter-Example

We study the relation between the stability of a competitive equilibrium (CE)and the price adjustment mechanism used to attain that equilibrium point.Using two specific examples, a three-commodity exchange economy with a uniquecompetitive equilibrium (Scarf's global instability example) and atwo-commodity, two-trader type exchange economy with multiple competitiveequilibria, we show that the stability of a CE depends critically upon thedynamics of the price adjustment mechanism. A particular CE may be unstableunder one price adjustment mechanism but stable under another. The jointdynamics of the chosen price adjustment mechanism and the given economydetermines the overall stability of its competitive equilibrium. Our resultssuggest that context-rich studies of economic systems which focus on aspecific price adjustment mechanism may provide insights into the dynamics andstability of economic systems that are often not revealed through acontext-independent analysis.     

Biomass and energy production in Casuarina equisetifolia plantation stands in the degraded dry tropics of the Vindhyan plateau, India

Two age groups of Casuarina equisetifolia (Forst.) plantation stands in the Renukoot forest division of the Vindhyan plateau were investigated over the span of three years for total and component biomass, annual net primary production, energy storage and annual net energy fixation. A high range of biomass (44–81 t ha⁻¹) was recorded in a densely populated stand at ages 5–7 years in comparison to a sparsely populated stand at ages 8–10 years. The contribution of the hole component gradually increased with increasing diameter class while foliage and branch components had a large proportion of biomass in the lower diameter classes. Maximum litterfall occurred in May and foliage litter contributed 87–95% of total litterfall. The energy content and storage in component parts were higher than some other promising tree species for energy plantation in the dry tropics. Production estimates of 19–29 t ha⁻¹ yr⁻¹ showed that the performance of Casuarina is good for dry tropical conditions. The biomass accumulation ratio and production efficiency showed a significant positive and negative (logarithmic) relationship, respectively with plantation age. The energy conserving efficiency of the 5-year old stand was more than twice that of the 8-year old stand.     

Minimum area circumscribing Polygons

We show that the smallestk-gon circumscribing a convexn-gon can be computed inO(n ² logn logk) time.     

Optimal tradeoffs for addition on systolic arrays

The complexity of adding twon-bit numbers on a two-dimensional systolic array is investigated. We consider different constraints on the systolic array, including:

whether or not the input and output ports lie on the periphery of the array,

constraints placed on the arrival and departure times of inputs and outputs

. For all combinations of the above constraints, we obtain optimal tradeoffs among the resources of area, pipeline delay, and worst-case time. It turns out that there is a subtle interplay among the constraints and some of our results seem counterintuitive. For instance, we show that allowing more-significant bits to arrive earlier than less-significant bits can speed up addition by a factor of logn. We also show that multiplexing can often result in a smaller array. On the other hand, we show that some known results, such as Chazelle and Monier's bounds for arrays that have input/output ports on the perimeter, also hold in less constrained models.     

Diamond like carbon films as a protective surface on PMMA for biomedical applications

Diamond like carbon films are deposited on PMMA using the Radio Frequency Plasma Enhanced Chemical Vapour Deposition technique with the variation of RF power at a constant pressure of 5 × 10⁻² mbar. Acetylene diluted with argon is used as a precursor for the deposition of DLC films. Deposited films are characterized using Raman, FTIR, optical contact angle technique and AFM. Optical contact angle is measured with water and blood of mice. It has been found that DLC coated PMMA is more hydrophobic compared to an uncoated surface. Samples are soaked with simulated body fluid for 30 days for the assessment of biocompatibility. Surface morphology of the samples before and after interaction with simulated body fluid has been studied by using AFM. The haemolysis test has also been carried out for the haemocompatibility assessment.     

Erosive Wear Characteristics of Plasma-Sprayed Coatings of Glass Microspheres Premixed With TiO2 Particles

In this article, plasma-sprayed coatings of borosilicate glass microspheres (BGM) premixed with TiO₂ particles in different proportions are deposited at various input power levels of the plasma torch. Erosion wear characteristics of these coatings are investigated following a plan of experiments based on the Taguchi technique, which is used to acquire the erosion test data in a controlled way. The study reveals that the impact velocity is the most significant among various factors influencing the wear rate of these coatings. An artificial neural network (ANN) approach is then implemented taking into account training and testing procedures to predict the triboperformance under different erosive wear conditions. This technique helps in saving time and resources for a large number of experimental trials and successfully predicts the wear rate of the coatings both within and beyond the experimental domain. This article proposes an integrated application of ANN and Taguchi's experimental design for analyzing and predicting the solid particle erosion wear response of a new class of coatings.